System and method for low peak to average power ratio multiple access communications

ABSTRACT

A method for generating a virtual codebook of low peak to average power ratio (PAPR) sequences includes generating a plurality of low PAPR combination block sequences, with each low PAPR combination block sequence including at least one of a plurality of sparse codebook, and applying time domain hopping to the plurality of low PAPR combination block sequences, thereby producing a virtual codebook. The method also includes storing the virtual codebook.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/521,387, filed on Oct. 22, 2014, which application is herebyincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to digital communications, andmore particularly to a system and method for low peak to average powerratio (PAPR) multiple access.

BACKGROUND

Recently, low density signature (LDS) and sparse code multiple access(SCMA) have been introduced as new multicarrier waveforms used formultiple access. Communications systems that utilize LDS or SCMAwaveforms can support system overloading (i.e., support more users thanthe available resources would otherwise support). Therefore, they areattractive waveform candidates in future technical standards such asenvisioned Fifth Generation (5G) communications systems for applicationsrequiring connectivity for very large numbers of devices, such as insome applications machine to machine (M2M) communications. In additionto supporting the ability to connect a large number of devices, some M2Mdeployments are also designed to make use of low cost devices.Therefore, there is a desire to provide connectivity for large numbersof low cost devices.

SUMMARY

Example embodiments of the present disclosure which provide a system andmethod for low peak to average power ratio (PAPR) multiple access.

In accordance with an example embodiment of the present disclosure, amethod for generating a virtual codebook of low peak to average ratio(PAPR) sequences of sparse codebooks is provided. The method includesgenerating, by a designing device, a plurality of low PAPR combinationblock sequences, with each low PAPR combination block sequence includingat least one of a plurality of sparse codebook, and applying, by thedesigning device, time domain hopping to the plurality of low PAPRcombination block sequences, thereby producing a virtual codebook. Themethod also includes storing, by the designing device, the virtualcodebook.

In accordance with another example embodiment of the present disclosure,a method for operating a transmitting device is provided. The methodincludes retrieving, by the transmitting device, a plurality of virtualcodebooks, each virtual codebook derived from a plurality of low peak toaverage power ratio (PAPR) combination block sequences, with each lowPAPR combination block sequence including at least one of a plurality ofsparse codebooks, and determining, by the transmitting device, anassignment of one of the plurality of virtual codebooks for thetransmitting device. The method also includes transmitting, by thetransmitting device, a packet towards a receiving device in accordancewith the assigned virtual codebook.

In accordance with another example embodiment of the present disclosure,a method for operating a receiving device is provided. The methodincludes retrieving, by the receiving device, a plurality of virtualcodebooks, each virtual codebook derived from a plurality of low peak toaverage power ratio (PAPR) combination block sequences, with each lowPAPR combination block sequence including at least one of a plurality ofsparse codebooks, and receiving, by the receiving device, a transmissionencoded in accordance with one of the plurality of virtual codebooks.

In accordance with another example embodiment of the present disclosure,a transmitting device is provided. The transmitting device includes aprocessor, and a transmitter operatively coupled to the processor. Theprocessor retrieves a plurality of virtual codebooks, each virtualcodebook derived from a plurality of low peak to average power ratio(PAPR) combination block sequences, with each low PAPR combination blocksequence including at least one of a plurality of sparse codebooks, anddetermines an assignment of one of the plurality of virtual codebook tothe transmitting device. The transmitter transmits a packet towards areceiving device in accordance with the assigned virtual codebook.

In accordance with another example embodiment of the present disclosure,a receiving device is provided. The receiving device includes aprocessor, and a receiver operatively coupled to the processor. Theprocessor retrieves a plurality of virtual codebooks, each virtualcodebook derived from a plurality of low peak to average power ratio(PAPR) combination block sequences, with each low PAPR combination blocksequence including at least one of a plurality of sparse codebooks. Thereceiver receives a transmission encoded in accordance with one of theplurality of virtual codebooks.

One advantage of an embodiment is that large numbers of combinationblock sequence usage patterns with low PAPR are available to supportmassive numbers of devices in a multi-carrier communications system.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example communications system according to exampleembodiments described herein;

FIG. 2 illustrates an example SCMA multiplexing scheme for encoding dataaccording to example embodiments described herein;

FIG. 3a illustrates an example arrangement of network resources used ina transmission of a data packet using wide-band SCMA and/or LDSaccording to example embodiments described herein;

FIG. 3b illustrates an example arrangement of network resources used ina transmission of a data packet using narrow-band SCMA and/or LDSaccording to example embodiments described herein;

FIG. 4 illustrates a flow diagram of example operations occurring in thedesigning and storing of virtual codebooks of combination blocksequences with low PAPR that are usable in SCMA and/or LDScommunications systems according to example embodiments describedherein;

FIG. 5 illustrates a flow diagram of example operations occurring in thedesigning of virtual codebooks of low PAPR combination block sequencesaccording to example embodiments described herein;

FIG. 6a illustrates example combination block sequences according toexample embodiments described herein;

FIG. 6b illustrates example virtual codebooks assigned to different UEs,wherein the virtual codebooks are formed from combination blocksequences that are two blocks in length using time domain hoppingaccording to example embodiments described herein;

FIG. 6c illustrates example virtual codebooks assigned to different UEswith frequency band hopping, wherein the virtual codebooks are formedfrom combination block sequences according to example embodimentsdescribed herein;

FIG. 7a illustrates a flow diagram of first example operations occurringin a transmitting device as the transmitting device communicates with areceiving device using SCMA and/or LDS with a virtual codebook accordingto example embodiments described herein;

FIG. 7b illustrates a flow diagram of second example operationsoccurring in a transmitting device as the transmitting devicecommunicates with a receiving device using SCMA and/or LDS with avirtual codebook according to example embodiments described herein;

FIG. 7c illustrates a flow diagram of third example operations occurringin a transmitting device as the transmitting device communicates with areceiving device using SCMA and/or LDS with a virtual codebook accordingto example embodiments described herein;

FIG. 8a illustrates a flow diagram of first example operations occurringin a receiving device as the receiving device communicates with atransmitting device using SCMA and/or LDS with a virtual codebookaccording to example embodiments described herein;

FIG. 8b illustrates a flow diagram of second example operationsoccurring in a receiving device as the receiving device communicateswith a transmitting device using SCMA and/or LDS with a virtual codebookaccording to example embodiments described herein;

FIG. 8c illustrates a flow diagram of third example operations occurringin a receiving device as the receiving device communicates with atransmitting device using SCMA and/or LDS with a virtual codebookaccording to example embodiments described herein;

FIG. 9 illustrates an example mapping of a virtual codebook to logicalresources and physical resources according to example embodimentsdescribed herein;

FIG. 10 illustrates an example first communications device according toexample embodiments described herein; and

FIG. 11 illustrates an example second communications device according toexample embodiments described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operating of the current example embodiments and the structurethereof are discussed in detail below. It should be appreciated,however, that the present disclosure provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificstructures of the disclosure and ways to operate the disclosure, and donot limit the scope of the disclosure.

One embodiment of the disclosure relates to low peak to average powerratio (PAPR) multiple access. For example, a designing device generatesa plurality of low PAPR combination block sequences, with each low PAPRcombination block sequence including at least one of a plurality ofsparse codebook, and applies time domain hopping (which should beunderstood to include combination block sequence hopping in the timedomain) to the plurality of low PAPR combination block sequences,thereby producing a virtual codebook. The designing device also storesthe virtual codebook.

The present disclosure will be described with respect to exampleembodiments in a specific context, namely SCMA and/or LDS communicationssystems that support connectivity for a large number of devices. Thedisclosure may be applied to standards compliant communications systems,such as those that are compliant with Third Generation PartnershipProject (3GPP), IEEE 802.11, and the like, technical standards, andnon-standards compliant communications systems, that use SCMA and/or LDSto support connecting a large number of devices.

As is known in the art, Code division multiple-access (CDMA) is amultiple access technique in which data symbols are spread out overorthogonal and/or near orthogonal code sequences. Traditional CDMAencoding is a two step process in which a binary code is mapped to aquadrature amplitude modulation (QAM) symbol before a spreading sequenceis applied. While traditional CDMA encoding can provide relatively highdata rates, new techniques/mechanisms for achieving even higher datarates are needed to meet the ever-growing demands of next-generationwireless networks. Low density spreading (LDS) is a form of CDMA usedfor multiplexing different layers of data. LDS uses repetitions of thesame symbol on layer-specific nonzero position in time or frequency. Asan example, in LDS-orthogonal frequency division multiplexing (OFDM) aconstellation point is repeated (with some possible phase rotations)over nonzero frequency tones of a LDS block.

Sparse code multiple access (SCMA) is a codebook-based non-orthogonalmultiplexing technique realized by super-imposing of multi-dimensionalcodewords selected form SCMA codebooks. Instead of spreading of QAMsymbols as in LDS, coded bits are directly mapped to multi-dimensionalsparse complex codewords. The major benefit of SCMA codebooks is theshaping gain of multi-dimensional constellations over repetition codingof LDS spreading. SCMA is classified as a waveform/modulation andmultiple access scheme. SCMA codewords are laid over multi-carrier tonessuch as OFDM. In SCMA overloading is achievable with moderate complexityof detection thanks to the sparseness of SCMA codewords. SCMA can shownoticeable gain over LDS especially for larger constellation sizes wherethe gain of constellation shaping is potentially larger. Even though LDSmay show poor link performance for larger constellation orders, itprovides system advantages due to its spreading and overloadingcapabilities. Interference whitening, open-loop user multiplexing andmassive connectivity are some examples showing the benefit of LDS fromsystem point of view. SCMA is a spreading and multiplexing techniquethat offers all the system benefits of LDS, while it maintains or evenimproves the link performance in comparison with OFDMA. Therefore, SCMAbrings the link advantages of OFDMA and system advantages of LDS allaltogether.

In SCMA, data is spread over multiple time-frequency tones of OFDMAresources through multi-dimensional codewords. Sparsity of codebooksused in SCMA helps to reduce the complexity of joint detection ofmultiplexed SCMA layers by using message passing algorithm (MPA). Ingeneral, each layer of SCMA has its specific codebook set. Low densityspreading (LDS) is a special case of SCMA. LDS as a form ofmulti-carrier CDMA (MC-CDMA) is used for multiplexing different layersof data. As opposed to SCMA which uses multi-dimensional codebooks, LDSuses repetitions of the same quadrature amplitude modulation (QAM)symbol on layer-specific nonzero position in time or frequency. Inapplications of LDS, signatures are used to spread data. As an example,in LDS-orthogonal frequency division multiplexing (LDS-OFDM) aconstellation point is repeated (with some possible phase rotations)over nonzero frequency tones of a LDS block. The shaping gain ofmulti-dimensional constellations is one of the advantages of SCMA overLDS. The gain is potentially high for higher order modulations where therepetition coding of LDS shows a large loss and poor performance.

SCMA is an encoding technique that encodes data streams, such as binarydata streams, or in general, M-ary data streams, where M is an integernumber greater than or equal to 2) into multidimensional codewords. SCMAdirectly encodes the data stream into multidimensional codewords andcircumvents quadrature amplitude modulation (QAM) symbol mapping, whichmay lead to coding gain over conventional CDMA (and LDS) encoding.Notably, SCMA encoding techniques convey data streams using amultidimensional codeword rather than a QAM symbol.

Additionally, SCMA encoding provides multiple access through the use ofdifferent codebooks for different multiplexed layers, as opposed to theuse of different spreading sequences for different multiplexed layers,e.g., a LDS signatures in LDS, as is common in conventional CDMAencoding. Furthermore, SCMA encoding typically uses codebooks withsparse codewords that enable receivers to use low complexity algorithms,such as message passing algorithms (MPA), to detect respective codewordsfrom combined codewords received by the receiver, thereby reducingprocessing complexity in the receivers. Hence, the codebooks used inSCMA to spread the data may be referred to as sparse codebooks, and inLDS (a special case of SCMA), sparse signatures may be used to refer tothe signatures used to spread the data.

As discussed previously, the ability to support overloading incommunications systems utilizing SCMA and/or LDS makes the twomulticarrier waveforms attractive for use in applications that requiremassive connectivity, such as M2M applications. However, themulticarrier nature of SCMA and LDS waveforms, as well as with othermulticarrier waveforms, such as orthogonal frequency divisionmultiplexing (OFDM), and the like, leads to communications with highPAPR. High PAPR communications generally require transmitters withexpensive and inefficient power amplifiers, which is counter to the lowcost devices targeted for M2M applications.

FIG. 1 illustrates an example communications system 100. Communicationssystem 100 may include an evolved NodeB (eNB) 105 operating as acommunications controller. Communications system 100 may also includeuser equipment (UE), such as UE 110, UE 112, UE 114, and UE 116. eNB 105may include multiple transmit antennas and multiple receive antennas tofacilitate MIMO operation, wherein a single eNB may simultaneouslytransmit multiple data streams to multiple users, a single user alsowith multiple receive antennas, or a combination thereof. Similarly, theUEs may include multiple transmit antennas and multiple receive antennasto support MIMO operation. In general, an eNB may also be referred to asa communications controller, a NodeB, a base station, a controller, andthe like. Similarly, a UE may also be referred to as a mobile device, amobile station, a mobile, a terminal, a user, a subscriber, and thelike. Communications system 100 may also include a relay node (RN) 118that is capable of utilizing a portion of resources of eNB 105 to helpimprove coverage and/or overall performance of communications system100.

While it is understood that communications systems may employ multipleeNBs capable of communicating with a number of UEs, only one eNB, oneRN, and a number of UEs are illustrated for simplicity.

A designing device 120 may design sparse signatures and/or sparsecodebooks for eNBs and/or UEs in communications system 100. Designingdevice 120 may also design virtual codebooks which may contain one ormore combination block sequences. The combination block sequences maycomprise one or more sparse codebooks (or sparse signatures in LDS) withlow PAPR to facilitate massive connectivity in SCMA and/or LDScommunications systems. Detailed descriptions of example embodiments fordesigning virtual codebooks of combination block sequences with low PAPRto facilitate massive connectivity are presented herein. Although shownin FIG. 1 as a stand-alone device, designing device 120 may beco-located with another entity in communications system 100, such as aneNB, or some other entity. Additionally, there may be multiple designingdevices, with each designing device designing sparse codebooks, sparsesignatures, virtual codebooks, and the like, for different portions ofcommunications system 100.

FIG. 2 illustrates an example SCMA multiplexing scheme 200 for encodingdata. As shown in FIG. 2, SCMA multiplexing scheme 200 may utilize aplurality of sparse codebooks, such as sparse codebook 210, sparsecodebook 220, sparse codebook 230, sparse codebook 240, sparse codebook250, and sparse codebook 260. Each sparse codebook of the plurality ofsparse codebooks is assigned to a different multiplexed layer. Eachsparse codebook includes a plurality of multidimensional codewords (orspreading sequences). It is noted that in SCMA, the multidimensionalcodewords are low density sequence signatures or similarly, sparsecodewords. More specifically, sparse codebook 210 includes codewords211-214, sparse codebook 220 includes codewords 221-224, sparse codebook230 includes codewords 231-234, sparse codebook 240 includes codewords241-244, sparse codebook 250 includes codewords 251-254, and sparsecodebook 260 includes codewords 261-264.

Each codeword of a respective sparse codebook may be mapped to adifferent data, e.g., binary, value. As an illustrative example,codewords 211, 221, 231, 241, 251, and 261 are mapped to binary value‘00’, the codewords 212, 222, 232, 242, 252, and 262 are mapped to thebinary value ‘01’, the codewords 213, 223, 233, 243, 253, and 263 aremapped to the binary value ‘10’, and the codewords 214, 224, 234, 244,254, and 264 are mapped to the binary value ‘11’. It is noted thatalthough the sparse codebooks in FIG. 2 are depicted as having fourcodewords each, SCMA sparse codebooks in general may have any number ofcodewords. As an example, SCMA sparse codebooks may have 8 codewords(e.g., mapped to binary values ‘000’ . . . ‘111’), 16 codewords (e.g.,mapped to binary values ‘0000’ . . . ‘1111’), or more.

As shown in FIG. 2, different codewords are selected from various sparsecodebooks 210, 220, 230, 240, 250, and 260 depending on the binary databeing transmitted over the multiplexed layer. In this example, codeword214 is selected from sparse codebook 210 because the binary value ‘11’is being transmitted over the first multiplexed layer, codeword 222 isselected from sparse codebook 220 because the binary value ‘01’ is beingtransmitted over the second multiplexed layer, codeword 233 is selectedfrom sparse codebook 230 because the binary value ‘10’ is beingtransmitted over the third multiplexed layer, codeword 242 is selectedfrom sparse codebook 240 because the binary value ‘01’ is beingtransmitted over the fourth multiplexed layer, codeword 252 is selectedfrom sparse codebook 250 because the binary value ‘01’ is beingtransmitted over the fifth multiplexed layer, and codeword 264 isselected from sparse codebook 260 because the binary value ‘11’ is beingtransmitted over the sixth multiplexed layer. Codewords 214, 222, 233,242, 252, and 264 may then be multiplexed together to form multiplexeddata stream 280, which is transmitted over shared resources of anetwork. Notably, codewords 214, 222, 233, 242, 252, and 264 are sparsecodewords, and therefore can be identified upon reception of multiplexeddata stream 280 using a low complexity algorithm, such as a messagepassing algorithm (MPA) or a turbo decoder.

As an example, consider an uplink pblock LDS/SCMA signal, where eachblock uses a signature/codeword of length K. Hence, this signal spans JKsubcarriers. Let b_(n), n=0,1, . . . , JK−1 denote the SCMA and/or LDSspread data associated with the n^(th) subcarrier, where b_(n) canassume value 0 due to the sparseness of the SCMA and/or LDS sparsecodebook and/or signature. The time domain SCMA and/or LDS signal isexpressible as

${x(t)} = {\frac{1}{\sqrt{JK}}{\sum\limits_{n = 0}^{{JK} - 1}{b_{n}{^{j\; 2\pi \frac{n}{T}t}.}}}}$

For discussion purposes, consider an LDS example where d=[d₀ d₁ . . .d_(J−1)]^(T) denotes a data symbol vector of length J and each symbol isspread using a signature s=[s₀ s₁ . . . s_(K−1)]^(T) (with |s|²=1). Inthis case, b=d

s is the data vector after LDS spreading, where

denotes Kronecker product operator and b_(n)=d_(j)s_(k), n=jK+k, j=0, .. . , J−1, k=0, . . . , K−1.

In the literature, the PAPR of x(t) is expressible as

${{PAPR} = \frac{\; {\max_{0 \leq t \leq T}{{x(t)}}^{2}}}{\frac{1}{T}{\int_{0}^{T}{{{x(t)}}^{2}{t}}}}},$

where

${{x(t)}}^{2} = {{\frac{1}{JK}{\sum\limits_{n = 0}^{{JK} - 1}{b_{n}}^{2}}} + {\frac{2}{JK}{{Re}\left( {\sum\limits_{n = 1}^{{JK} - 1}{\rho_{n}^{j\; 2\; \pi \frac{n}{T}t}}} \right)}}}$

is the instantaneous power of x(t), with

$\frac{1}{JK}{\sum\limits_{n = 0}^{{JK} - 1}{b_{n}}^{2}}$

being the average power, and ρ_(n)≦Σ_(k=0) ^(JK−n−1)b_(k)b_(k+n)*, n=0,1, . . . , JK−1 being the aperiodic autocorrelation of b_(n). Then, itmay be possible to express PAPR as

${PAPR} = {\max_{0 \leq t \leq T}{\left( {1 + \frac{2{{Re}\left( {\sum\limits_{n = 1}^{{JK} - 1}{\rho_{n}^{j\; 2\pi \frac{n}{T}t}}} \right)}}{\sum\limits_{n = 0}^{{JK} - 1}{b_{n}}^{2}}} \right).}}$

In order to obtain some insight on the PAPR of SCMA and/or LDS signals,a simple PAPR analysis of a 1-block signal using a signature with 2non-zero elements is discussed herein. That is, consider J=1, K=4, N=2,i.e., d=d₀, s=[0 |s₁|e^(jφ) ¹ 0 |s₃|e^(jφ) ³ ]^(T), so that b=d₀·[0|s₁|e^(jφ) ¹ 0 |s₃|e^(jφ) ³ ]^(T), where

[ρ₀ ρ₁ ρ₂ ρ₃ ]=|d ₀|²·[1 0 |s ₁ |·|s ₃ |e ^(j(φ) ¹ ^(−φ) ³ ⁾ 0],

and

${{Re}\left( {\sum\limits_{n = 1}^{{JK} - 1}{\rho_{n}^{j\; 2\; \pi \frac{n}{T}t}}} \right)} = {{{s_{1}} \cdot {s_{3}}}{{\cos \left( {{2\pi \frac{2}{T}t} + \left( {\phi_{1} - \phi_{3}} \right)} \right)}.}}$

Hence, the PAPR of this signal is expressed as 1+2·|s₁|·|s₃|. It can beshown that the PAPR is maximum at 3 dB when |s₁|=|s₃|=1/√{square rootover (2)}, and minimum at 0 dB when either |s₁| or |s₃| equals 0 (i.e.,the system is reduced to a single carrier system). This is trueregardless of spreading pattern (e.g., signature and/or codeword) lengthK, as well as the phases and positions of non-zero elements. For SCMA,since there is power imbalance in non-zero subcarriers of a codeword(e.g., |s₁|≠|s₃|), the PAPR of 1-block SCMA signal is lower than that ofLDS signal (i.e., |s₁|=|s₃|). However, for multiple-block SCMA and/orLDS, the interaction between phases of multiple data symbols and thoseof the signatures/codewords make the PAPR of SCMA and/or LDS signalsdata-dependent. Therefore, the complementary cumulative distributionfunction (CCDF) of the PAPR is considered. The CCDF of the PAPR is theprobability that the PAPR is higher than a given PAPR threshold,PAPR_(Th), i.e., CCDF(PAPR)=Pr(PAPR>PAPR_(Th))), over all possible datacombinations (i.e., applicable for small block size). For a larger blocksizes, the CCDF of PAPR may be obtained using simulation, such as MonteCarlo simulation. Moreover, PAPR_(99.9%) denotes the 99.9-percentilePAPR and may be defined as Pr(PAPR>PAPR_(99.9%))=10⁻³.

According to an example embodiment, narrow-band SCMA and/or LDS is usedto transmit a data packet. Typically, for a data packet of given size,transmission on a narrow-band channel will take longer than transmissionon a wide-band channel. However, in some applications, such as wheremassive connectivity and very low PAPR are requirements, long delays canbe tolerated.

FIG. 3a illustrates an example arrangement 300 of network resources usedin a transmission of a data packet using wide-band SCMA and/or LDS. Ingeneral, network resources may include time resources (such as timeslots as specified for a frequency band), frequency resources (such asfrequency bands as specified for a time slot), or a combination of bothtime resources and frequency resources (such as multiple frequency bandsand multiple time slots). As its name implies, wide-band SCMA and/or LDSmakes use of a relatively large number of frequency resources totransmit a data packet. Since many frequency resources, shown in FIG. 3aas F, are available to transmit the data packet, a relatively smallamount of time resources, shown in FIG. 3a as T, are needed. Typically,as F is increased, T decreases as long as the amount of data transmittedremains constant. A portion of the data packet carried in atime-frequency resource, such as time-frequency resource 305, may bespread using a signature. As shown in FIG. 3a , a single signature S1 isused for spreading the portions of the data packet in all of thetime-frequency resources.

FIG. 3b illustrates an example arrangement 350 of network resources usedin a transmission of a data packet using narrow-band SCMA and/or LDS. Asshown in FIG. 3b , a relatively small number of frequency resources,shown in FIG. 3b as f, with f<<F, are available to transmit the datapacket. Since f is small, the number of time resources, shown in FIG. 3bas t, needed to transmit the data packet is large (assuming that thedata packets transmitted in FIG. 3a and FIG. 3b are equal in size). Ingeneral, the number of time resources may be expressible as

t=F/f*T.

As an illustrative example, if F/f is equal to 4, then t is 4*T. Again,a single signature S1 is used for spreading the portions of the datapacket in all of the time-frequency resources.

As discussed previously, in order to support some applications (such asM2M applications), the ability to connect a large number of devices andvery low PAPR may enable a variety of different deployment scenarios.However, SCMA and/or LDS transmissions are generally high PAPRtransmissions due to their multicarrier nature. Therefore, there is aneed for massive connectivity and very low PAPR in SCMA and/or LDScommunications systems in order to support such applications.

According to an example embodiment, a system and method for low PAPRcommunications is provided. The system and method designs virtualcodebooks of combination block sequences (sparse codebook or sparsesignature sequences used to spread data being transmitted) with low PAPRthat are usable in SCMA and/or LDS communications system. The system andmethod supports communications between a transmitting device and areceiving device using the virtual codebooks of combination blocksequences.

FIG. 4 illustrates a flow diagram of example operations 400 occurring inthe designing and storing of virtual codebooks of combination blocksequences with low PAPR that are usable in SCMA and/or LDScommunications systems. Operations 400 may be indicative of operationsoccurring in the designing and storing of combination block sequences,such as by a designing device, for example, a stand-alone designingdevice (e.g., designing device 120) or a co-located designing device(e.g., a co-located designing device located in an eNB or a networkentity), as the designing device designs and stores virtual codebooks ofcombination block sequences with low PAPR that are usable in SCMA and/orLDS communications systems.

Operations 400 may begin with the designing of virtual codebooks of lowPAPR combination block sequences (block 405). The designing of thevirtual codebooks of low PAPR combination block sequences may begin withthe application of signature and/or codebook hopping to sparse codebooksor sparse signatures to produce available combination block sequences(i.e., to increase a number of combination block sequences) and thenapplying one or more phase rotation techniques to the availablecombination block sequences to optimize a PAPR for each of the availablecombination block sequences. Since not all of the available combinationblock sequences have low (or sufficiently low) PAPR (even after PAPRoptimization), a specified number of available combination blocksequences with PAPR that meet a specified PAPR threshold may beselected, thereby producing low PAPR combination block sequences. Thevirtual codebooks may be formed from the low PAPR combination blocksequences by using combination block sequence hopping in the time domain(referred to herein as time domain hopping). Detailed discussion ofexample techniques for designing virtual codebooks of combination blocksequences with low PAPR are presented below. The virtual codebooks oflow PAPR combination block sequences may be stored for subsequent use(block 410). The virtual codebooks of low PAPR combination blocksequences may be stored in a memory local to the designing device. Thevirtual codebooks of low PAPR combination block sequences may be storedin memories of transmitting devices and/or receiving devices. Thevirtual codebooks of low PAPR combination block sequences may be storedin a remote database. The virtual codebooks of low PAPR combinationblock sequences may be provided to communications devices, such as eNBs,UEs, and the like.

FIG. 5 illustrates a flow diagram of example operations 500 occurring inthe designing of virtual codebooks of low PAPR combination blocksequences. Operations 500 may be indicative of operations occurring inthe designing of virtual codebooks of low PAPR combination blocksequences, for example, in a designing device, such as a stand-alonedesigning device (e.g., designing device 120) or a co-located designingdevice (e.g., a co-located designing device located in an eNB or anetwork entity), as the designing device designs virtual codebooks oflow PAPR combination block sequences. Operations 500 may be an exampleembodiment of designing virtual codebooks of low PAPR combination blocksequences, block 405 of FIG. 4.

Operations 500 may begin with the designing device applying signatureand/or codebook hopping to sparse codebooks to produce availablecombination block sequences (block 505). As an illustrative example, thedesigning device may retrieve the sparse codebooks from a local orremote memory and apply signature and/or codebook hopping in thefrequency domain to the sparse codebooks to produce the combinationblock sequences. As an illustrative example, consider a situation wherethe combination block sequences of length two blocks generated from 6sparse codebooks denoted S1, S2, S3, S4, S5, and S6. The application ofthe signature and/or codebook hopping to the sparse codebooks may yielda total of 6²=36 combination block sequences (each two blocks long) ofsparse codebooks, with a first example combination block sequencecomprising S1:S1 (shown in FIG. 6a as combination block sequence 605), asecond example combination block sequence comprising S1:S2 (shown inFIG. 6a as combination block sequence 607), a third example combinationblock sequence being S1:S3 (shown in FIG. 6a as combination blocksequence 609), and so on, to a 36-th example combination block sequencebeing S6:S6 (shown in FIG. 6a as combination block sequence 611).

FIG. 6a illustrates example combination block sequences 600. Combinationblock sequences 600 include combination block sequences that are twoblocks long that are generated from 6 sparse codebooks (and/orsignatures). It is noted that S1, S2, S3, S4, S5, and S6 are shorthandnotation for the distinct sparse codebooks, and that actual sparsecodebooks may be sequences of values, such as 1, 0, −1, and the like.

Referring back now to FIG. 5, the designing device may apply a phaserotation to the available combination block sequences of sparsecodebooks to produce PAPR optimized combination block sequences (block510). According to an example embodiment, one or more of a variety ofphase rotations may be applied to each of the available combinationblock sequences. Examples of the phase rotations include a Newman Phaserotation, a Shroeder Phase rotation, a Modified Shroeder Phase rotation,and the like. The Newman Phase rotation may be expressed mathematicallyas

${\varphi_{n} = \frac{{\pi \left( {n - 1} \right)}^{2}}{JK}},$

-   -   n=0, . . . , JK−1        where K is the index of the subcarriers after SCMA and/or LDS        spreading.

-   The Shroeder Phase rotation may be expressed mathematically as:

φ_(l)′=φ_(l−1)′+2π(n _(l) −n _(l−1))Σ_(m=1) ^(l−1) p _(n) _(m) , l=1, .. . , JN,

where it is assumed that φ₀′=0 without loss of generality. For flatspectrum, p_(n) _(l) =1/JN, l=1, . . . , JN, where n_(l) denotes theindex of l^(th) non-zero subcarrier and p_(n) _(l) be the normalizedpower associated with the subcarrier.

-   The modified Shroeder Phase rotation may be expressed mathematically    as:

φ_(l)″=φ_(l−1)″+2πΣ_(m=1) ^(l−1) p _(n) _(m) , l=1, . . . , JN,

where for flat spectrum,

${p_{n_{L}} = \frac{1}{L}},{\varphi_{1}^{''} = {\frac{{\pi \left( {I - 1} \right)}^{2}}{L}.}}$

Although the application of the phase rotations to the availablecombination block sequences may yield an optimized PAPR for each of theavailable combination block sequences of sparse signatures, not all ofthe PAPR optimized combination block sequences have low PAPR,especially, not all of the PAPR optimized combination block sequencesmay have a PAPR low enough to meet M2M application requirements. Thedesigning device may evaluate the PAPR optimized combination blocksequences and select the PAPR optimized combination block sequences thatmeet a PAPR threshold (block 515). The selected combination blocksequences may be referred to as low PAPR combination block sequences. Asan illustrative example, the designing device may determine a PAPR foreach of the PAPR optimized combination block sequences and compare thePAPRs for the PAPR optimized combination block sequences against thePAPR threshold. The designing device may select the PAPR optimizedcombination block sequences with PAPRs meeting the PAPR threshold (e.g.,lower than the PAPR threshold). The PAPR threshold may be a predefinedvalue that is specified by a technical standard, an operator of acommunications system that includes the designing device, and the like.As an illustrative example, a fixed PAPR threshold may be 3 dB. The PAPRthreshold may be adaptable, allowing for increases or decreases to meetperformance metrics of the communications system. As an illustrativeexample, the PAPR threshold may be set according to device, e.g.,receiving device and/or transmitting device, capability, such as radiofrequency (RF) chain capability, battery capacity, and the like. If thedevice capability is poor, the PAPR threshold may be decreased, while ifthe device capability is high, the PAPR threshold may be increased toallow for more combination block sequences and support for more devices.

The selection of PAPR optimized combination block sequences with PAPRthat meet the PAPR threshold can substantially reduce the number ofcombination block sequences available for use in SCMA and/or LDScommunications. As an illustrative example, referring back to theexample discussed above wherein available combination block sequencesthat are two blocks in length are generated from 6 sparse signaturesand/or sparse codebooks, if the PAPR threshold is 3 dB, perhaps only 6out of the 36 combination block sequences generated by the applicationof the phase rotation meet or exceed the PAPR threshold and may bereferred to as low PAPR combination block sequences. Collectively, theapplication of the signature and/or codebook hopping (block 505), theapplication of the phase rotation (block 510), and the selection of thePAPR optimized combination block sequences may be referred to asgenerating low PAPR combination block sequences.

The designing device may apply time domain hopping to the low PAPRcombination block sequences to increase the number of low PAPRcombination block sequences available for communications, producingvirtual codebooks of combination block sequences (block 520). Timedomain hopping may involve the use of potentially different low PAPRcombination block sequences in different time resources to help increasethe number of different virtual codebooks, and therefore, reduce theprobability of codeword and/or signature collisions within each SCMA orLDS block. The application of time domain hopping to the low PAPRcombination block sequences produces virtual codebooks of combinationblock sequences, each of which specifies a sequence of low PAPRcombination block sequences over time.

FIG. 6b illustrates example virtual codebooks 630 assigned to differentUEs, wherein the virtual codebooks are formed from combination blocksequences that are two blocks in length using time domain hopping. It isnoted that each of the virtual codebooks shown in FIG. 6b are used over2 blocks (SCMA or LDS), with the same 2 blocks for all UEs. Furthermore,the combination block sequences shown in FIG. 6b are low PAPRcombination block sequences, such as after phase optimization. As shownin FIG. 6 b, virtual codebook 635 (assigned to UE2) comprisescombination block sequence S2:S2, with virtual codebook 635 beingrepeated as needed. Similarly, virtual codebook 640 (assigned to UE4)also comprises combination block sequence S2:S2, with virtual codebook640 being repeated as needed. This results in collisions in every blockused in transmissions by UE2 and UE4.

Also shown in FIG. 6 b, virtual codebook 645 (assigned to UE5) compriseslow PAPR combination block sequences: S1:S3; S2:S1; and S3:S2; andvirtual codebook 645 is repeated. As an example, the first fewrepetitions of virtual codebook 645 may be:

-   -   S1:S3; S2:S1; S3:S2; S1:S3; S2:S1; S3:S2; S1:S3; S2:S1; S3:S2; .        . . .        Similarly, virtual codebook 650 (assigned to UE6) comprises low        PAPR combination block sequences: S3:S2; S1:S3; and S2:S1; and        virtual codebook 650 is repeated. This results in no collisions        between transmissions of UE5 and UE6, and relatively few        collisions with UE1 through UE4.

Referring back to FIG. 5, typically, the application of time domainhopping may be described as follows:

-   -   Select a sequence of one or more low PAPR combination block        sequences of sparse signatures as a virtual codebook. Hence, the        virtual codebook may be one or more low PAPR combination block        sequences in length. The sequence of one or more low PAPR        combination block sequences may be selected in accordance with        time domain hopping, random selection, pseudo-random selection,        and the like. It is noted that the virtual codebook may include        one or more repetitions of the sequence of one or more low PAPR        combination block sequences.

As an illustrative example of the use of time domain hopping to selectthe sequence of one or more low PAPR combination block sequences, referback to the example with 36 combination block sequences shown in FIG. 6aand assume that after PAPR optimization and selection using a PAPRthreshold, the resulting low PAPR combination block sequences comprisesequences: S1:S1; S2:S2; S3:S3; S1:S3; S2:S1; and S3:S2. Time domainhopping selects low PAPR combination block sequences to populateelements of virtual codebooks. Therefore, for each element of a virtualcodebook, one of the low PAPR combination block sequences is selected.To understand time domain hopping, consider an example virtual codebookwith 3 elements (the virtual codebook may also be said to be a length 3virtual codebook): time domain hopping may result in selecting one ofthe low PAPR combination block sequences for a first element of thevirtual codebook, another one of the low PAPR combination blocksequences for a second element of the virtual codebook, and yet anotherone of the low PAPR combination block sequences for a third element ofthe virtual codebook. The same or different low PAPR combination blocksequences may be selected for the different elements of the virtualcodebook. Example virtual codebooks may include:

-   -   Virtual Codebook 1: (S1:S1); (S1:S1); (S1:S1),    -   Virtual Codebook 2: (S2:S2); (S2:S2); (S2:S2),    -   Virtual Codebook 3: (S3:S3); (S3:S3); (S3:S3),    -   Virtual Codebook 4: (S1:S3); (S2:S1); (S3:S2),    -   Virtual Codebook 5: (S3:S2); (S1:S3); (S2:S1),    -   Virtual Codebook 6: (S2:S1); (S3:S2); (S1:S3), and the like.    -   In the use of a virtual codebook, the virtual codebook may be        scaled with a scaling until a resulting sequence of the virtual        codebook meets a length threshold. The length threshold may be a        non-negative integer value that is at least as long as a longest        expected packet transmission in terms of time resources. As an        example, if the packet being transmitted occupies 30 time domain        resource allocations (also referred to as a time resource), the        sequence of low PAPR combination block sequences used to        transmit the packet in accordance with the virtual codebook may        need to be 30 combination block sequences long (one combination        block sequence for each time based resource allocation). Hence,        if the virtual codebook is 3 combination block sequences long        (e.g., S3:S2; S1:S3; and S2:S1), then the virtual codebook is        scaled by a scaling factor equal to 10 to produce a sequence of        combination block sequences that is of sufficient length, while        if the virtual codebook is 6 combination block sequences long,        then the virtual codebook is scaled by a scaling factor equal to        5 times to produce a sequence of combination block sequences        that is of sufficient length. When the scaling factor is an        integer value greater than 1, the virtual codebook may be        repeated (scaling factor) times, while when the scaling factor        is a non-integer value greater than 1 (e.g., 1½, 5¾, 3⅓, and the        like), the virtual codebook may be repeated (INT(scaling        factor)) times and truncated by (FRACTION(scaling factor)),        where function INT( ) returns an integer portion of a        non-integer value and FRACTION( ) returns a fractional portion        of the non-integer value.    -   Similarly, if the virtual codebook is longer than the number of        time domain resources need to transmit the packet, the virtual        codebook may be truncated by the scaling factor, which may be a        real number smaller than 1. As an illustrative example, if the        virtual codebook is 10 combination block sequences long and a        packet transmission requires 6 time resources, the scaling        factor is equal to 6/10 and the first 6 combination block        sequences of virtual codebook may be used. It is noted that any        sequence of 6 combination block sequences of the virtual        codebook may be used while preserving low PAPR properties.

According to an example embodiment, the application of time domainhopping to the low PAPR combination block sequences may produce a largenumber virtual codebooks. Each of the virtual codebooks may be specifiedby its sequence of low PAPR combination block sequences (e.g., S1S3;S2:S1; and S3:S2). As an example, the virtual codebook used by UE1 ofFIG. 6b may include low PAPR combination block sequence S1:S1, while UE5may include low PAPR combination block sequence S1S3; S2:S1; and S3:S2for its virtual codebook, and UE6 may include low PAPR combination blocksequence S3:S2; S1:S3; and S2:S1 for its virtual codebook. Each of thevirtual codebooks used by the UEs shown in FIG. 6b may be scaled to meetthe requirements of the illustrated packet transmissions. However, itmay not be necessary to scale a virtual codebook if the virtual codebookis of sufficient length.

According to an example embodiment, a virtual codebook is specified byits sequence of low PAPR combination block sequences. Additionally, ifthe length of the virtual codebook is insufficient for a transmission,it is extended by a scaling factor to meet the requirements of thetransmission. As an illustrative example, a virtual codebook of length 5is automatically scaled by a scaling factor equal to 6 for thetransmission of a packet that requires 30 time resources, while ascaling factor equal to 2 for the transmission of a packet that requires10 time resources. For non-integer scaling factors, the virtual codebookmay be truncated by the fractional portion of the non-integer scalingfactor. As an illustrative example, for a packet that requires 22 timeresources, a virtual codebook of length 5 may be scaled by a scalingfactor of 4.4, meaning that the virtual codebook is repeated 4 timesplus 4/10-th of the combination block sequences of the virtual codebook.Similarly, if the transmission of a packet requires fewer time resourcesthan the length of the virtual codebook, the virtual codebook may bescaled by a scaling factor smaller than 1 utilizing truncation, forexample. As an illustrative example, if a transmission of a packetrequires 7 time resources, a virtual codebook of length 10 may be scaledby a scaling factor equal to 0.7.

According to an example embodiment, the virtual codebooks may bespecified by a technical standard, an operator of the communicationssystem, an agreement between communications devices, and the like. Thevirtual codebooks may have fixed length, and may be periodic in nature.Different virtual codebooks may have different lengths. Differentvirtual codebooks may have different periodicities. In practice, inorder to minimize storage requirements, the virtual codebooks may bestored in their shortest non-repeated form and then extended to meetlength requirements. As an illustrative example, if a first virtualcodebook is defined from a single low PAPR combination block sequence(therefore, the first virtual codebook has a periodicity of 1), but isto be used in a situation where 5 time resources are need, then thevirtual codebook may be repeated a total of 5 times to meet the lengthrequirement. However, when stored, only the single low PAPR combinationblock sequence needs to be saved. Similarly, if a second virtualcodebook is defined from two low PAPR combination block sequences(therefore, the second virtual codebook has a periodicity of 2), but isto be used in a situation where 5 time resources are needed, then thevirtual codebook may be repeated a total of 2.5 times to meet the lengthrequirement. However, when stored, only the two low PAPR combinationblock sequences are saved.

The communicating devices may share information about the virtualcodebook to help simplify virtual codebook detection at a receivingdevice. According to an alternative example embodiment, the virtualcodebooks may be random (or pseudo-random) in nature. If the virtualcodebooks are random or pseudo-random, blind detection may be used at areceiving device to detect transmissions. Blind detection may involvethe receiving device attempting to decode transmissions intime-frequency resources using each low PAPR combination block sequenceas a decoding hypothesis. In general, the only time that the decoding ofthe transmission is successful is when the receiving device uses thesame low PAPR combination block sequence in its decoding as was used tospread the data at the transmitting device. According to anotheralternative example embodiment, some communications devices may utilizevirtual codebooks of specified sequences, while others may utilizevirtual codebooks of randomly generated sequences.

According to an example embodiment, frequency band hopping may beapplied to increase frequency diversity. In frequency band hopping,transmissions may be assigned to network resources in differentfrequency bands that may be spaced relatively far apart in frequency toallow a receiving device to exploit frequency diversity to help improveoverall communications performance. In the different frequency bands,the transmissions may be made using the low PAPR combination blocksequences and/or the virtual codebooks. FIG. 6c illustrates examplevirtual codebooks 660 assigned to different UEs with frequency bandhopping, wherein the virtual codebooks are formed from low PAPRcombination block sequences. The assignment of virtual codebooks in afirst frequency band may simply be a duplicate of the assignment ofvirtual codebooks in a second frequency band, such as shown in FIG. 6 c.Alternatively, the assignment of virtual codebooks in a first frequencyband may be different from the assignment of virtual codebooks in asecond frequency band. Alternatively, some UEs may be assigned the samevirtual codebooks in different frequency bands, while other UEs may beassigned different virtual codebooks in different frequency bands.Alternatively, portions of a virtual codebook may be assigned toresources in different frequency bands.

FIG. 7a illustrates a flow diagram of first example operations 700occurring in a transmitting device as the transmitting devicecommunicates with a receiving device using SCMA and/or LDS with avirtual codebook. Operations 700 may be indicative of operationsoccurring in a transmitting device, such as an eNB or a UE, as thetransmitting device communicates with a receiving device using SCMAand/or LDS with a virtual codebook.

Operations 700 may begin with the transmitting device retrieving virtualcodebooks of low PAPR combination block sequences (block 705). Accordingto an example embodiment, the transmitting device may retrieve thevirtual codebooks from a memory located in the transmitting device.According to another example embodiment, the transmitting device mayretrieve the virtual codebooks from a remote memory or database.According to another example embodiment, the virtual codebooks of lowPAPR combination block sequences are generated in a random orpseudo-random manner and the transmitting device may retrieve low PAPRcombination block sequences from a local memory or a remote memory or aremote data base.

The transmitting device may determine an assignment of a virtualcodebook for itself (the transmitting device) (block 707). According toan example embodiment, the transmitting device may retrieve theassignment from a memory, a local or remote database, and the like.According to an example embodiment, the transmitting device may make theassignment of the virtual codebook. According to an example embodiment,the assignment of the virtual codebooks may be based on devicecapability. As an example, a device with a low capability transmitter ora low capacity battery may be assigned a virtual codebook with aparticularly low PAPR. According to another example embodiment, theassignment of the virtual codebooks may be based on a type of thetransmitting device. As an example, different virtual codebooks may beassigned according to transmitting device type, such as personalcomputer, smart telephone, sensor, M2M device, and the like. Accordingto yet another example embodiment, the assignment of the virtualcodebooks may be based on geo-location information of the transmittingdevice. As an example, different virtual codebooks may be assigned basedon distance from receiving device, sector of a sectorized antenna, andthe like. According to yet another example embodiment, the assignment ofthe virtual codebooks may be based on traffic type, traffic priority,device priority, channel condition, and the like.

The transmitting device may send an indication of the virtual codebookassigned to the transmitting device to the receiving device (block 709).According to an example embodiment, both the transmitting device and thereceiving device have access to the virtual codebooks, e.g., stored in alocal memory, and the indication may be an index of the virtual codebookassigned to the transmitting device. According to another exampleembodiment, the transmitting device may transmit a sequence of low PAPRcombination block sequences (or an indication thereof) to the receivingdevice. The transmitting device may transmit to the receiving deviceusing the assigned virtual codebook (block 711). As discussedpreviously, transmitting to the receiving device may involve thetransmitting device spreading a packet being transmitted to thereceiving device using the assigned virtual codebook and transmittingthe spread packet to the receiving device.

Since an assigned virtual codebook typically comprises a fixed number oflow PAPR combination block sequences, the assigned virtual codebook maybe either too long or too short for the transmission and/or reception ofsome packets. If the assigned virtual codebook is too long, the assignedvirtual codebook may be scaled with a scaling factor smaller than 1 toproduce the proper number of combination block sequences. As anillustrative example, if the transmitting device is transmitting apacket over 10 time resources and the assigned virtual codebookcomprises 30 low PAPR combination block sequences, the transmittingdevice may scaled with a scaling factor equal to 10/30, truncating theassigned virtual codebook to 10 low PAPR combination block sequences.Generally, the truncation used will preserve low PAPR qualities, but itmay be possible to select other sub-sequences in the assigned virtualcodebook. While, if the assigned virtual codebook is too short, theassigned virtual codebook may be scaled with a scaling factor greaterthan 1 to produce the proper number of low PAPR combination blocksequences. As an illustrative example, if the transmitting device istransmitting a packet over 90 time resources and the assigned virtualcodebook comprises 30 combination block sequences, the transmittingdevice may scale the virtual codebook with a scaling factor of 3. Asdiscussed previously, scaling factors may also be non-integer values,which means that the virtual codebooks are repeated the INT(scalingfactor) times and combined with a truncated version of the virtualcodebook truncated by FRACTION(scaling factor).

Similarly, a virtual codebook may be generated from low PAPR combinationblock sequences with a fixed block length each (e.g., the virtualcodebooks shown in FIGS. 6 a, 6 b, and 6 c are generated from low PAPRcombination block sequences with a block length of 2). However, asituation may arise where low PAPR combination block sequences withdifferent block lengths are needed. In such a situation, the virtualcodebook may be modified by increasing or shortening the length of thelow PAPR combination block sequences in the virtual codebook.Alternatively, multiple sets of virtual codebooks, with each set beingdesigned from low PAPR combination block sequences of different blocklengths, may be available for use in such situations. The use of virtualcodebooks with low PAPR combination block sequences with block lengthsthat match the needed block length ensures that the low PAPR propertiesare optimized.

According to an example embodiment, operations associated with blocks705, 707, and 709 are performed at a controlling device instead of thetransmitting device. The controlling device may be the transmittingdevice, or the receiving device. The controlling device may also be analternate device not directly involved in the communications between thetransmitting device and the receiving device, but is responsible forassigning the virtual codebook (s) to the transmitting device.

FIG. 7b illustrates a flow diagram of second example operations 750occurring in a transmitting device as the transmitting devicecommunicates with a receiving device using SCMA and/or LDS with avirtual codebook. Operations 750 may be indicative of operationsoccurring in a transmitting device, such as an eNB or a UE, as thetransmitting device communicates with a receiving device using SCMAand/or LDS with a virtual codebook.

Operations 750 may begin with the transmitting device retrieving virtualcodebooks (block 755). According to an example embodiment, thetransmitting device may retrieve the virtual codebooks from a memorylocated in the transmitting device. According to another exampleembodiment, the transmitting device may retrieve the virtual codebooksfrom a remote memory or database. According to another exampleembodiment, the sequence of low PAPR combination block sequences of thevirtual codebook is generated in a random or pseudo-random manner andthe transmitting device may retrieve the low PAPR combination blocksequences from a local memory or a remote memory or a remote data base.

The transmitting device may determine an assignment of a virtualcodebook for the transmitting device (block 757). According to anexample embodiment, the transmitting device may retrieve the assignmentfrom a memory, a local or remote database, and the like. According to anexample embodiment, the assignment of the virtual codebooks may be basedon device capability. As an example, a device with a low capabilitytransmitter or a low capacity battery may be assigned a virtual codebookwith a particularly low PAPR. According to another example embodiment,the assignment of the virtual codebooks may be based on a type of thetransmitting device. As an example, different virtual codebooks may beassigned according to transmitting device type, such as personalcomputer, smart telephone, sensor, M2M device, and the like. Accordingto yet another example embodiment, the assignment of the virtualcodebooks may be based on geo-location information of the transmittingdevice. As an example, different virtual codebooks may be assigned basedon distance from receiving device, sector of a sectorized antenna, andthe like. According to yet another example embodiment, the assignment ofthe virtual codebooks may be based on traffic type, traffic priority,device priority, channel condition, and the like.

As discussed previously, it may be possible for the receiving device touse blind detection with possible low PAPR combination block sequencesas hypotheses to decode the transmissions made by the transmittingdevice without having knowledge of the virtual codebook being used bythe transmitting device. Therefore, the transmitting device may transmitto the receiving device using the assigned virtual codebook withouthaving to send an indication of the virtual codebook assigned to thereceiving device (block 759). Additionally, if the transmitting deviceis using a random or pseudo-random technique for time domain hopping,the transmitting device may not have a priori knowledge of the virtualcodebook, preventing the transmitting device from informing thereceiving device of the virtual codebook.

According to an example embodiment, operations associated with blocks755, and 757, are performed at a controlling device instead of thetransmitting device. The controlling device may be the transmittingdevice, or the receiving device. The controlling device may also be analternate device not directly involved in the communications between thetransmitting device and the receiving device, but is responsible forassigning the virtual codebook(s) to the transmitting device.

FIG. 7c illustrates a flow diagram of third example operations 775occurring in a transmitting device as the transmitting devicecommunicates with a receiving device using SCMA and/or LDS with avirtual codebook. Operations 775 may be indicative of operationsoccurring in a transmitting device, such as an eNB or a UE, as thetransmitting device communicates with a receiving device using SCMAand/or LDS with a virtual codebook.

Operations 775 may begin with the transmitting device retrieving virtualcodebooks of low PAPR combination block sequences (block 780). Accordingto an example embodiment, the transmitting device may retrieve thevirtual codebooks from a memory located in the transmitting device.According to another example embodiment, the transmitting device mayretrieve the virtual codebooks from a remote memory or database.According to another example embodiment, the sequence of low PAPRcombination block sequences of the virtual codebook is generated in arandom or pseudo-random manner and the transmitting device may retrievethe low PAPR combination block sequences from a local memory or a remotememory or a remote data base.

The transmitting device may receive an assignment of a virtual codebookfor the transmitting device (block 782). According to an exampleembodiment, the assignment of the virtual codebook may be made by areceiving device and the receiving device may send an indicator ofassignment to the transmitting device. Since the assignment of thevirtual codebook is made by the receiving device, the transmittingdevice does not need to send an indicator of the assignment to thereceiving device. The transmitting device may transmit to the receivingdevice using the assigned virtual codebook (block 784).

FIG. 8a illustrates a flow diagram of first example operations 800occurring in a receiving device as the receiving device communicateswith a transmitting device using SCMA and/or LDS with a virtualcodebook. Operations 800 may be indicative of operations occurring in areceiving device, such as an eNB or a UE, as the receiving devicecommunicates with a transmitting device using SCMA and/or LDS with avirtual codebook.

Operations 800 may begin with the receiving device retrieving virtualcodebooks of low PAPR combination block sequences (block 805). Accordingto an example embodiment, the receiving device may retrieve the virtualcodebooks from a memory located in the receiving device. According toanother example embodiment, the receiving device may retrieve thevirtual codebooks from a remote memory or database.

The receiving device may receive an indication of an assigned virtualcodebook (block 807). According to an example embodiment, the indicationmay be an index of the virtual codebook assigned to the transmittingdevice. According to another example embodiment, the indication may beof a virtual codebook out of a plurality of possible virtual codebooks,a sequence of low PAPR combination block sequences out of a plurality ofsequences of low PAPR combination block sequences, and the like. Thereceiving device may receive and decode a transmission from thetransmitting device using the assigned virtual codebook (block 809). Asan illustrative example, receiving and decoding the transmission fromthe transmitting device may involve detecting a transmission in networkresources assigned to the receiving device and using the sparsecodebooks (or sparse signatures) associated with the assigned virtualcodebook to decode the transmission.

Since assigned virtual codebook typically comprises a fixed number oflow PAPR combination block sequences, the assigned virtual codebook maybe either too long or too short for the transmission and/or reception ofsome packets. If the assigned virtual codebook is too long, the assignedvirtual codebook may be truncated to the proper number of low PAPRcombination block sequences. As an illustrative example, if thereceiving device is receiving a packet transmission over 10 timeresources and the assigned virtual codebook comprises 30 low PAPRcombination block sequences, the receiving device may scale the assignedvirtual codebook with a scaling factor of 10/30 to produce 10 low PAPRcombination block sequences, with the use of a truncation function, forexample. Generally, the truncation used will preserve low PAPRqualities, but it may be possible to select other sub-sequences in theassigned virtual codebook. While, if the assigned virtual codebook istoo short, the assigned virtual codebook may be scaled with a scalingfactor greater than 1 to produce the proper number of low PAPRcombination block sequences. As an illustrative example, if thereceiving device is receiving a packet transmission over 90 time domainresources and the assigned virtual codebook comprises 30 low PAPRcombination block sequences, the receiving device may scale the virtualcodebook with a scaling factor of 3.

FIG. 8b illustrates a flow diagram of second example operations 850occurring in a receiving device as the receiving device communicateswith a transmitting device using SCMA and/or LDS with a virtualcodebook. Operations 850 may be indicative of operations occurring in areceiving device, such as an eNB or a UE, as the receiving devicecommunicates with a transmitting device using SCMA and/or LDS with avirtual codebook.

Operations 850 may begin with the receiving device retrieving virtualcodebooks of low PAPR combination block sequences (block 855). Accordingto an example embodiment, the receiving device may retrieve the virtualcodebooks of low PAPR combination block sequences from a memory locatedin the receiving device. According to another example embodiment, thereceiving device may retrieve the virtual codebooks of low PAPRcombination block sequences from a remote memory or database.

As discussed previously, the receiving device may use blind detectionwith possible low PAPR combination block sequences (e.g., from thevirtual codebook) as hypotheses to decode the transmissions made by thetransmitting device without having knowledge of the virtual codebookactually being used by the transmitting device. Therefore, the receivingdevice may receive and decode a transmission from the transmittingdevice using blind detection without having to receive an indication ofthe virtual codebook assigned to the transmitting device (block 857).

FIG. 8c illustrates a flow diagram of third example operations 875occurring in a receiving device as the receiving device communicateswith a transmitting device using SCMA and/or LDS with a virtualcodebook. Operations 875 may be indicative of operations occurring in areceiving device, such as an eNB or a UE, as the receiving devicecommunicates with a transmitting device using SCMA and/or LDS with avirtual codebook.

Operations 875 may begin with the receiving device retrieving virtualcodebooks of low PAPR combination block sequences (block 880). Accordingto an example embodiment, the receiving device may retrieve the virtualcodebooks of low PAPR combination block sequences from a memory locatedin the receiving device. According to another example embodiment, thereceiving device may retrieve the virtual codebooks of low PAPRcombination block sequences from a remote memory or database.

The receiving device may determine an assignment of a virtual codebookfor the transmitting device (block 882). According to an exampleembodiment, the assignment of the virtual codebooks may be based ontransmitting device capability. As an example, a device with a lowcapability transmitter or a low capacity battery may be assigned avirtual codebook with a particularly low PAPR. According to anotherexample embodiment, the assignment of the virtual codebooks may be basedon a type of the transmitting device. As an example, different virtualcodebooks may be assigned according to transmitting device type, such aspersonal computer, smart telephone, sensor, M2M device, and the like.According to yet another example embodiment, the assignment of thevirtual codebooks may be based on geo-location information of thetransmitting device. As an example, different virtual codebooks may beassigned based on distance from receiving device, sector of a sectorizedantenna, and the like. According to yet another example embodiment, theassignment of the virtual codebooks may be based on traffic type,traffic priority, device priority, channel condition, and the like.

The receiving device may send an indication of the virtual codebookassigned to the transmitting device (block 884). According to an exampleembodiment, both the transmitting device and the receiving device haveaccess to the virtual codebooks, e.g., stored in a local memory, and theindication may be an index of the virtual codebook assigned to thetransmitting device. According to another example embodiment, thereceiving device may transmit an indication of a sequence of low PAPRcombination block sequences making up the virtual codebook out of aplurality of low PAPR sequences of combination block sequences, and thelike, to the transmitting device. The receiving device may receive anddecode a transmission from the transmitting device using the assignedvirtual codebook (block 886). As an illustrative example, receiving anddecoding the transmission from the transmitting device may involvedetecting a transmission in network resources assigned to the receivingdevice and using the sparse codebooks and/or sparse signaturesassociated with the assigned virtual codebook to decode thetransmission.

FIG. 9 illustrates a diagram 900 highlighting an example mapping of avirtual codebook to logical resources and physical resources. As shownin FIG. 9, a virtual codebook 905 includes a sequence of low PAPRcombination block sequences. The low PAPR combination block sequences ofvirtual codebook 905 may be assigned to logical resources (shown inhighlight 910). The logical resources include time resources andfrequency resources. It is noted that, as shown in FIG. 9, virtualcodebook 905 is not long enough to cover the time resources, so virtualcodebook 905 is repeated twice, with the second repetition of virtualcodebook 905 being truncated. The logical resources (shown in highlight910) may be mapped to physical resources (shown in highlight 915). Thephysical resources include physical time resources and physicalfrequency resources. As shown in FIG. 9, the logical resources may bemapped to physical resources that belong in different frequency bands.Although shown in FIG. 9 as being mapped to physical resources ofmultiple frequency bands, a different mapping may result in the logicalresources being mapped to physical resources of a single frequency band.

FIG. 10 illustrates an example first communications device 1000.Communications device 1000 may be an implementation of a transmittingdevice, such as a communications controller, such as an eNB, a basestation, a NodeB, a controller, and the like, a UE, such as a user, asubscriber, a terminal, a mobile, a mobile station, and the like, thatincludes a co-located designing device or a stand-alone designingdevice. Communications device 1000 may be used to implement various onesof the embodiments discussed herein. As shown in FIG. 10, a transmitter1005 is configured to transmit frames, combination block sequences,indications, and the like. Communications device 1000 also includes areceiver 1010 that is configured to receive frames, and the like.

A spreading pattern hopping unit 1020 is configured to apply codebookand/or signature hopping to sparse codebooks (or sparse signatures) togenerate available combination block sequences of sparse codebooks. Aphase rotating unit 1021 is configured to apply phase rotations, such asNewman Phase rotations, Shroeder Phase rotations, modified ShroederPhase rotations, and the like, to available combination block sequencesto optimize PAPR for the available combination block sequences. Aselecting unit 1022 is configured to select the PAPR optimizedcombination block sequences as generated by phase rotating unit 1021that have a PAPR that meets a PAPR threshold and produce low PAPRcombination block sequences. A time hopping unit 1024 is configured toapply time domain hopping to the low PAPR combination block sequences toproduce virtual codebooks of low PAPR combination block sequences thatmay be assigned to transmitting devices. The use of time domain hoppinggenerally generates more virtual codebooks than the number of low PAPRcombination block sequences, the number of receiving devices that can besupported may be increased. Time hopping unit 1024 is configured toproduce virtual codebooks of low PAPR combination block sequences. Afrequency band hopping unit 1026 is configured to make use of frequencyband hopping to increase frequency diversity. In situations wheremultiple frequency bands are available, frequency band hopping unit 1026increases frequency diversity by using frequency bands that arerelatively far apart for transmissions to receiving devices. A codebookassigning unit 1028 is configured to assign a virtual codebook to atransmitting device. Codebook assigning unit 1028 is configured to makeuse of factors, including device capability, device types, geo-locationinformation, traffic types, traffic priorities, receiving devicepriorities, channel condition, and the like, to assign the virtualcodebooks. An indicating unit 1030 is configured to generate anindication of the selected virtual codebook. As an example theindication includes a representation of the assigned virtual codebook, asequence of combination block sequences of the assigned virtualcodebook, and the like. A scaling unit 1032 is configured to scale avirtual codebook by a scaling factor. A memory 1040 is configured tostore sparse signatures and/or sparse codebooks, combination blocksequences of sparse codebooks, low PAPR combination block sequences,PAPRs, PAPR thresholds, virtual codebooks, frequency band hoppinginformation, indicators, scaling factors, and the like.

The elements of communications device 1000 may be implemented asspecific hardware logic blocks. In an alternative, the elements ofcommunications device 1000 may be implemented as software executing in aprocessor, controller, application specific integrated circuit, or soon. In yet another alternative, the elements of communications device1000 may be implemented as a combination of software and/or hardware.

As an example, receiver 1010 and transmitter 1005 may be implemented asa specific hardware block, while spreading pattern hopping unit 1020,phase rotating unit 1021, sequence selecting unit 1022, time hoppingunit 1024, frequency band hopping unit 1026, codebook assigning unit1028, indicating unit 1030, and a scaling unit 1032 may be softwaremodules executing in a microprocessor (such as processor 1015) or acustom circuit or a custom compiled logic array of a field programmablelogic array. Spreading pattern hopping unit 1020, phase rotating unit1021, sequence selecting unit 1022, time hopping unit 1024, frequencyband hopping unit 1026, codebook assigning unit 1028, indicating unit1030, and a scaling unit 1032 may be modules stored in memory 1040.

FIG. 11 illustrates an example second communications device 1100.Communications device 1100 may be an implementation of a receivingdevice, such as a communications controller, such as an eNB, a basestation, a NodeB, a controller, and the like, or a UE, such as a user, asubscriber, a terminal, a mobile, a mobile station, and the like.Communications device 1100 may be used to implement various ones of theembodiments discussed herein. As shown in FIG. 11, a transmitter 1105 isconfigured to transmit frames, and the like. Communications device 1100also includes a receiver 1110 that is configured to receive frames,combination block sequences, indications, and the like.

An indication processing unit 1120 is configured to process an indicatorof a virtual codebook. Indication processing unit 1120 is configured toretrieve the virtual codebook from a memory using the virtual codebookinformation, for example. Indication processing unit 1120 is configuredto generate an indication of a virtual codebook selected for atransmitting device. A sequence processing unit 1122 is configured togenerate sequences of low PAPR combination block sequences of virtualcodebooks used in decoding a received transmission from the virtualcodebook information. Sequence processing unit 1122 is configured toscale virtual codebooks by scaling factors. A blind detecting unit 1124is configured to decode network resources by performing blind detectionusing different low PAPR combination block sequence hypotheses on thenetwork resources. Blind detecting unit 1124 is configured to performblind detection until the transmission is successfully decoded or untillow PAPR combination block sequence as hypotheses are exhausted. Amemory 1140 is configured to store sparse codebooks and/or sparsesignatures, combination block sequences, frequency band hoppinginformation, indicators, virtual codebooks, and the like.

The elements of communications device 1100 may be implemented asspecific hardware logic blocks. In an alternative, the elements ofcommunications device 1100 may be implemented as software executing in aprocessor, controller, application specific integrated circuit, or soon. In yet another alternative, the elements of communications device1100 may be implemented as a combination of software and/or hardware.

As an example, receiver 1110 and transmitter 1105 may be implemented asa specific hardware block, while indication processing unit 1120,sequence processing unit 1122, and blind detecting unit 1124 may besoftware modules executing in a microprocessor (such as processor ills)or a custom circuit or a custom compiled logic array of a fieldprogrammable logic array. Indication processing unit 1120, sequenceprocessing unit 1122, and blind detecting unit 1124 may be modulesstored in memory 1140.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims.

What is claimed is:
 1. A method for generating a virtual codebook of lowpeak to average ratio (PAPR) combination block sequences of sparsecodebooks, the method comprising: generating, by a designing device, aplurality of low PAPR combination block sequences, with each low PAPRcombination block sequence including at least one of a plurality ofsparse codebook; applying, by the designing device, time domain hoppingto the plurality of low PAPR combination block sequences, therebyproducing a virtual codebook; and storing, by the designing device, thevirtual codebook.
 2. The method of claim 1, wherein storing the virtualcodebook further comprises storing the virtual codebook in a remotememory.
 3. The method of claim 1, wherein the virtual codebook comprisesa sequence of at least one low PAPR combination block sequence.
 4. Themethod of claim 1, wherein generating the plurality of low PAPRcombination block sequences comprises: optimizing PAPR values associatedwith each of a plurality of available combination block sequences; andselecting candidate combination block sequences from the plurality ofavailable combination block sequences with optimized PAPR values thatmeet a PAPR threshold, thereby producing the plurality of low PAPRcombination block sequences.
 5. The method of claim 4, whereinoptimizing the PAPR values comprises applying a phase rotation to eachof the plurality of available combination block sequences.
 6. The methodof claim 5, wherein applying the phase rotation comprises applying oneof a Newman Phase rotation, a Shroeder Phase rotation, or a modifiedShroeder Phase rotation to each of the plurality of availablecombination block sequences.
 7. The method of claim 4, furthercomprising applying codebook hopping to the plurality of sparsecodebooks to produce the plurality of available combination blocksequences.
 8. The method of claim 1, wherein the plurality of sparsecodebooks comprise sparse code multiple access (SCMA) codebooks.
 9. Themethod of claim 1, wherein the plurality of sparse codebooks comprisesparse low density sequence (LDS) signatures.
 10. The method of claim 1,wherein storing the virtual codebook further comprises storing thevirtual codebook in a memory of a transmitting or receiving device. 11.A designing device for generating a virtual codebook of low peak toaverage ratio (PAPR) combination block sequences of sparse codebooks,the designing device comprising: at least one processor; and anon-transitory computer readable storage medium storing programming forexecution by the at least one processor, the programming includinginstructions for: generating a plurality of low PAPR combination blocksequences, with each low PAPR combination block sequence including atleast one of a plurality of sparse codebook; applying time domainhopping to the plurality of low PAPR combination block sequences,thereby producing a virtual codebook; and storing the virtual codebook.12. The designing device of claim 11, wherein the instructions forstoring the virtual codebook comprise instructions for storing thevirtual codebook in a remote memory.
 13. The designing device of claim11, wherein the virtual codebook comprises a sequence of at least onelow PAPR combination block sequence.
 14. The designing device of claim11, wherein the instructions for generating the plurality of low PAPRcombination block sequences comprise instructions for: optimizing PAPRvalues associated with each of a plurality of available combinationblock sequences; and selecting candidate combination block sequencesfrom the plurality of available combination block sequences withoptimized PAPR values that meet a PAPR threshold, thereby producing theplurality of low PAPR combination block sequences.
 15. The designingdevice of claim 14, wherein the instructions for optimizing the PAPRvalues comprise instructions for applying a phase rotation to each ofthe plurality of available combination block sequences.
 16. Thedesigning device of claim 15, wherein the instructions for applying thephase rotation comprise instructions for applying one of a Newman Phaserotation, a Shroeder Phase rotation, or a modified Shroeder Phaserotation to each of the plurality of available combination blocksequences.
 17. The designing device of claim 14, wherein the programmingincludes further instructions for applying codebook hopping to theplurality of sparse codebooks to produce the plurality of availablecombination block sequences.
 18. The designing device of claim 11,wherein the plurality of sparse codebooks comprise sparse code multipleaccess (SCMA) codebooks.
 19. The designing device of claim 11, whereinthe plurality of sparse codebooks comprise sparse low density sequence(LDS) signatures.
 20. The designing device of claim 11, wherein theinstructions for storing the virtual codebook comprise instructions forstoring the virtual codebook in a memory of a transmitting or receivingdevice.